脑缺血导致轴突病变形成的机制研究

Ischemic stroke is usually occurred in the brain's white matter in humans such as internal capsule, which mainly contains the projection fibers and glial cells. Why the functional defects or loss of these fibers are difficult to repair after brain ischemia? Our recent studies have demonstrated that transient focal cerebral schemia/reperfusion induces early and chronic axonal changes in rats, suggesting that axonopathy may be an important mechanism contributing to the functional defects or loss，and being difficult to repair after ischemic stroke. However, the detailed mechanisms are unknown on how brain ischemia induces axonopathy and affects its restoration. In this proposal, by combining different cell and animal models with different techniques and methods, we will investigate: (1) the relationships between the Na+、K+ or Ca2+ ions including their channels and the formation of axonopathy, and the posible roles of the change of axonal transport by using cultured cotical and hipocampal neurons and brain slices; (2) how the change of the mitochondrial functions and the interactions betweew the axons and oligodendrocytes are involoved in the chronic axonopathy induced by cerebral ischemia. Our study may provide a new idea for the ischemic stroke treatment.

缺血性脑中风常常发生在脑白质区如内囊，那里含有的主要是投射纤维和神经胶质细胞。但这些神经纤维在脑缺血后导致的功能障碍或缺失为什么难以修复。我们最近的研究表明，短暂性的脑缺血再灌注导致了明显的早期出现和长期存在的轴突病变。由此我们推测，轴突病变可能是缺血脑中风后功能障碍和缺失并难以恢复的重要病理机制。可是，脑缺血是如何导致轴突病变，以及影响其修复的确切机制是不清楚的。本项目将使用细胞和动物模型结合不同的研究方法和手段探讨：（1）使用培养的大鼠脑片和脑皮层及海马神经细胞建立氧-葡萄糖剥夺导致的轴突病变模型来阐明Na+、K+ 和Ca2+ 钙离子及通道与轴突病变形成的关系以及轴突转运功能改变可能参与的作用；（2）阐明轴突线粒体功能改变以及少突胶质细胞与轴突的相互作用异常是如何参与脑缺血导致的长期存在的轴突病变。我们的研究可能为缺血性脑中风的治疗提供新的思路。

本课题研究目的：研究小鼠硫铵素缺乏（TD）处理后相关脑区的轴突改变情况并探讨与阿尔茨海默病（AD）病理机制的联系。方法：将维生素B1拮抗剂分别立体定位注射入APP/PS1双转基因及野生小鼠（C57BL/6）右侧的海马齿状回，内嗅皮层及前皮质区，建立脑区TD动物模型。于TD处理后第10天进行动物行为学检测,并应用免疫荧光、神经示踪技术、Western-blot及RT-PCR观察脑区内轴突的形态学、tau蛋白和Aβ表达的改变。结果：TD处理后动物的主，被动规避行为与对照组相比有显著下降（P<0.05）,TD处理后两种小鼠脑区内磷酸化tau蛋白，Aβ呈现高表达，注射脑区及其投射脑区内呈现轴突肿胀，有膨体甚至出现“轴突漏”。APP/PS1双转基因小鼠在TD处理后加速“老年斑”的生成。结论：TD处理引起的轴突病变与阿尔茨海默病的传统病理发生和发展过程存在正相关。